Question

Given $x+y=-6$ and $y-4x=4$ are the two equations. If $(x,y)$ satisfies the system of equations , find the value of $xy$.

• A. $8$
• B. $-8$
• C. $9$
• D. $7$

Answer 1

The correct option is A $8$

Let $x+y=-6$.................(1)

and $-4x+y=4$..............(2)

Subtract (1) by (2), we get

$\Rightarrow 5x=-10$

$\Rightarrow x=-2$

Put the value of $x=-2$ in (1)

$\Rightarrow -2+y=-6$

$\Rightarrow y=-6+2$

$\Rightarrow y=-4$

$\therefore xy=-2\times -4=8$